LUMBRICUS 111 



seminal vesicles, which will be studied in connection with the 

 reproductive organs. Press these aside and notice the small 

 calciferous glands. 



3. The esophagus leads to the crop, which lies just an- 

 terior to and in contact with the gizzard. In what somites 

 are these organs placed? What is their shape? Do you 

 understand the function of each? 



4. Leaving the gizzard is the stomach-intestine, which runs 

 through the remainder of the body, giving off lateral diver- 

 ticula in each somite. Do you know its function? 



Notice the relation of the septa to the alimentary canal. 



Circulatory System. — 1. Lying dorsal to the alimentary 

 canal is the blood vessel that could be seen pulsating in the 

 living specimen. In most cases this vessel is full of blood 

 and appears brown. 



2. Near the anterior end of the body large side branches, 

 the aortic arches, are given off on either side and pass down 

 around the esophagus. How many aortic arches do you find? 

 In what somites are they placed? 



3. Examine with a lens and see whether you find other 

 vessels connected with the dorsal aorta. If you do, determine 

 how they are placed. Do they appear like the aortic arches? 



Make a drawing of the anterior end of the body, showing 

 the points you have seen. 



4. Gently press the stomach-intestine to one side and see 

 if you find a blood vessel beneath it. Do the aortic arches 

 join this? Other connections between blood vessels are too 

 small to be studied in dissections, but you should understand 

 from textbooks or lectures what they are, and the probable 

 course of circulation. 



Excretory System. — 1. A pair of nephridia occurs in each 

 somite, one nephridium on either side of the alimentary 

 canal. (The first three or four somites are not provided with 

 nephridia.) Each nephridium is a coiled tube, appearing to 

 the unaided eye as a fluffy mass, that opens externally be- 

 tween the groups of setae, in the position already observed, 

 and internally by a small opening near the funnel. The inner 



